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arXiv 2403.03074astro-ph.GA
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南天区大质量恒星形成区相关致密核的物理性质与运动学

Physical Properties and Kinematics of Dense Cores Associated with Regions of Massive Star Formation from the Southern Sky

L. E. Pirogov, P. M. Zemlyanukha, E. M. Dombek, M. A. Voronkov

备注：
49 pages, 10 figures
发表信息：
Astronomy Reports, 2023, volume 67, no. 12, p.p. 1355-1380
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AI总结：

利用MOPRA-22m对南天6个大质量恒星形成相关致密核进行84–92 GHz观测，估算物理参数并通过非LTE模型揭示G268.42–0.85核的异常收缩运动。

摘要：

本文给出了南天区6个含有致密核并与大质量恒星及星团形成区相关的天体在约84–92 GHz频率范围内的光谱观测结果。观测使用MOPRA-22m射电望远镜进行。在局地热力学平衡（LTE）近似框架下，计算了H$^{13}$CN、H$^{13}$CO$^+$、HN$^{13}$C、HC$_3$N、c-C$_3$H$_2$、SiO、CH$_3$C$_2$H和CH$_3$CN分子的柱密度和丰度。得到了动力学温度（约30–50 K）、发射区尺度（约0.2–3.1 pc）和维里质量（约70–4600 $M_{\odot}$）的估计值。三个核中的线宽随距中心距离的增加而减小。在四个核中，观测到光学厚谱线HCO$^+$(1-0)和HCN(1-0)的轮廓存在不对称性，表明沿视线方向存在系统性运动。在两个例子中，这种不对称性可能由气体收缩引起。在非LTE球对称模型框架下获得的HCO$^+$(1-0)和H$^{13}$CO$^+$(1-0)模型光谱图与观测图进行了拟合。计算了G268.42–0.85核中密度（$\propto r^{-1.6}$）、湍流速度（$\propto r^{-0.2}$）和收缩速度（$\propto r^{0.5}$）的径向剖面。该收缩速度剖面既不同于气体向原恒星自由下落情况下的预期剖面（$\propto r^{-0.5}$），也不同于整体核坍缩情况下的预期剖面（收缩速度与距离无关）。本文对所得结果进行了讨论。

英文摘要：

The results of spectral observations in the $\sim 84-92$ GHz frequency range of six objects in the southern sky containing dense cores and associated with regions of massive stars and star clusters formation are presented. The observations were carried out with the MOPRA-22m radio telescope. Within the framework of the local thermodynamic equilibrium (LTE) approximation, the column densities and abundances of the H$^{13}$CN, H$^{13}$CO$^+$, HN$^{13}$C, HC$_3$N, c-C$_3$H$_2$, SiO, CH$_3$C$_2$H and CH$_3$CN molecules are calculated. Estimates of kinetic temperatures ($\sim 30-50$ K), sizes of emission regions ($\sim 0.2-3.1$ pc) and virial masses ($\sim 70-4600~M_{\odot}$) are obtained. The line widths in the three cores decrease with increasing distance from the center. In four cores, asymmetry in the profiles of the optically thick lines HCO$^+$(1-0) and HCN(1-0) is observed, indicating the presence of systematic motions along the line of sight. In two cases, the asymmetry can be caused by contraction of gas. The model spectral maps of HCO$^+$(1-0) and H$^{13}$CO$^+$(1-0), obtained within the framework of the non-LTE spherically symmetric model, are fitted into the observed ones. The radial profiles of density ($\propto r^{-1.6}$), turbulent velocity ($\propto r^{-0.2}$), and contraction velocity ($\propto r^{0.5}$) in the G268.42--0.85 core have been calculated. The contraction velocity profile differs from that expected both in the case of free fall of gas onto a protostar ($\propto r^{-0.5}$), and in the case of global core collapse (contraction velocity does not depend on distance). A discussion of the obtained results is provided.

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